9v Battery Voltage Monitor - This circuit turns on a LED whenever the voltage of a standard 9v battery connected to the circuit drops below 7.2 volts. it uses a LTC1440 comparator, which also contains a 1.18v reference diode. in standby mode, the circuit draws only 4uA. . . Circuit by David Johnson P.E.-July, 2006

AC Line Under/Over Voltage Alarm - Power lines, which deviate much beyond normal voltages can damage expensive electronic equipment. The circuit below sounds an alarm whenever the line voltage is higher or lower than normal. I set the alarm limits at about +-15% from standard levels . . . Hobby Circuit designed by David Johnson P.E.-March, 2009

µC measures High-frequency signals - 03/02/98 EDN Design Ideas: (File contains many circuits, please scroll to find this one) To measure a high-frequency signal using an 8-bit µC, the time period of the measured frequency must be relatively close to the internal clock of the µC. For example, if the internal clock period is 1 sec, then. __ Circuit Design by Stan D'Souza, Microchip Technology Inc, Chandler, AZ

1.5V, 7A Bus Termination - 09/14/95 EDN Design Ideas: Some of the newest high-performance processors require a 1.5V bus terminator that can source currents as high as 7A. This terminator requires a very fast transient response, because the device must react to high peak-current changes that have extremely fa __ Circuit Design by Chester Simpson and Mineo Yamatake, National Semiconductor, Santa Clara, CA

20 Segment Expanded Scale Voltmeter - This is an Expanded Scale Voltmeter based on the National LM3914 chip. it is a 0.25 volt range between each LED. __ Designed by G.L. Chemelec

8 LEDs Make a 100-Division Voltmeter - 09/22/11 EDN Design Ideas: Use a counter IC to drive two sets of four LEDs. The circuit in this Design idea makes a voltmeter that reads to 0.99V. The idea uses a counter IC to drive two sets of four LEDs (Figure 1). Each of these two sets represents a BCD (binary-coded-decimal) value. With all of the LEDs off, the voltmeter reads 0V. With all of the LEDs on, the reading is 0.99V. Op amp IC 1A generates a predictable voltage ramp. __ Circuit Design by Raju Baddi, Tata Institute of Fundamental Research, Pune University, Maharashtra, India

3 Digits Digital Volt Meter with PIC16F676 - This is simple 3-digits digital volt meter. PIC 16F676 used to read analog signal (voltage) and display the value on 3-digits 7-segment. You can apply similar principles to measure DC current with parallel R shunt. __

3-Digit Volt/ Amper Meter - Even if the digital multimeters have dominated in a lot of applications, in the measurement, exist the need for existence of instruments of clue in various appliances, voltage and current, as in power supply or elsewhere. The circuits that give make this precisely the work, measure the voltage in terminal a circuit and the current that passes in his. The circuit does not present particular difficulties for somebody that has a small experience. The two circuits are the himself, with a small difference only in their input, when they have they measure voltage or current and in connection that concern decimal point. __

500 V Common-Mode Voltage Current Monitor - The input voltage to the AD7171 ADC is converted into an offset binary code at the output of the ADC. The code is processed in the PC by using the SDP hardware board and LabViEW Evaluation software in Figure 3. __ Analog Devices from the Lab

9v Battery Voltage Monitor - This circuit turns on a LED whenever the voltage of a standard 9v battery connected to the circuit drops below 7.2 volts. it uses a LTC1440 comparator, which also contains a 1.18v reference diode. in standby mode, the circuit draws only 4uA. . . Circuit by David Johnson P.E.-July, 2006

A svelte beast cuts high voltage down to size - 11/24/99 EDN Technical Article: Piezoceramic transformers have many features, including small form factor, that make them inherently well-suited to CCFL-backlight inverters. __ Circuit Design by Jim Williams and J Phillips and G Vaughn, im Williams, EDN's most revered contributor-At 63 years of age, Williams passed away in June 2011 after a stroke.

AC Line Under/Over Voltage Alarm - Power lines, which deviate much beyond normal voltages can damage expensive electronic equipment. The circuit below sounds an alarm whenever the line voltage is higher or lower than normal. I set the alarm limits at about +-15% from standard levels . . . Hobby Circuit designed by David Johnson P.E.-March, 2009

AC Power Line Voltage Indicator - The solidstate voltmeter circuit described here indicates the mains voltage with a resolution that is comparable to that of a general-purpose analogue voltmeter. The status of the mains voltage is available in the form of an LED bar graph__ Electronics Projects for You

An RF Voltmeter for Transceiver Servicing - This project was published in the November 2010 issue of the Australian magazine "Amateur Radio", and has been designed using parts which are very readily available __ Designed by VK5JST / VK5TR

Analog Milliamp Meter Used as Voltmeter - A milliamp meter can be used as a volt meter by adding a series resistance. The resistance needed is the full scale voltage reading divided by the full scale current of the meter movement. So, if you have a 1 milliamp meter and you want to read 0-10 volts you will need a total resistance of 10/.001 = 10K ohms. The meter movement itself will have a small resistance __ Designed by Bill Bowden

AVR Digital Voltmeter - We build a simple and inexpensive three digit display. it's a voltmeter module but it has also general purpose digital iO pins. You could use it as well to read a digital sensor and display the value. it can be freely programmed, calibrated and even be programmed with a non linear formula. it's a display where you can define the relation between the measured value and the displayed number. __ Designed by Guido Socher

Battery Monitor Draws 8 µA or Les - 04/13/95 EDN Design Ideas: The battery monitor in Fig 1 nominally draws 5 µA during normal operation and flashes an alarm indicator when the battery voltage drops below a critical value. The alarm-state current depends on the desired indicator brightness, but you can easily make the current average less than 500 µA. This monitor was developed as a change-battery warning __ Circuit Design by Arthur W Du Rea Jr, Science Applications International Corp, Oak Ridge, TN

Battery Monitor Emulates Auto Dashboard - 07/03/97 EDN Design Ideas: When you use battery-powered scientific-recording equipment, you must know the state of the battery, because an unnoticed battery run-down can lead to loss of data. Several types of warning indicators are available, but all have their drawbacks. Moving-coil indicators, test terminals, and digital flags, for example, __ Circuit Design by TG Barnett and J Millar, University of London, UK

Build a Digital Audio Millivoltmeter - Versatile unit indicates signal levels in mV, dBv & dbm. Want to measure small signals at audio frequencies? Here's a low-cost digital audio millivoltmeter which will allow you to measure audio signals from below 5Hz to above 100kHz. As well as indicating the level in both millivolts and dBV, it also shows the corresponding dBm level into 600 ohms.__ SiliconChip

Circuit Detects & Disconnects Overvoltage - 04/25/96 EDN Design Ideas: The circuit in Fig.1 protects circuits and systems with power supplies that may exceed safe limits. One example is small consumer products that use external ac adapters; it's easy to mistakenly plug in the wrong adapter. Another example is a portable system that uses a rechargeable battery pack. if the battery pack is absent or fails to open during recharging, a high-compliance charger can deliver excessive voltages to the system __ Circuit Design by Kerry Lacanette, National Semiconductor Corp, Santa Clara, CA

Circuit Detects DC Ringing - 08/17/00 EDN Design Ideas: Ring detection is a common task in telephony-related digital design. The goal is to sense an ac ringing voltage applied to the telephone line by a central office or PBX (private branch exchange) and then pass an appropriate signal to the µC or µP __ Circuit Design by Jerzy Chrzaszcz, Warsaw Institute of Technology, Poland

Circuit Detects first event - 05/03/01 EDN Design Ideas: The circuit in Figure 1 is a "first-event" indicator, like a game show's "who's first to answer" detector. it indicates which of the two momentary switches, S 1 or S 2 , closes first by latching the corresponding channel, IC A or IC B , to a high state. A __ Circuit Design by Kelly Flaherty, National Semiconductor, San Mateo, CA

Circuit Detects reset source - 04/27/00 EDN Design Ideas: Embedded single-board computers do not rely only on power-on resets; they often use multiple sources to reset CPUs to prevent CPUs from being locked into endless loops. However, in most cases, CPUs start from the starting points of memories to fetch their first code, because they have no way of knowing what generated the reset. The circuit in Figure 1 allows a CPU to know the source of a reset. __ Circuit Design by Shyam Tiwari

Circuit Detects total on-time - 02/04/99 EDN Design Ideas: NOTE: Page includes several designs. Scroll to find this one. The circuit in Figure 1 provide as a voltage that is directly proportional to the sum of the total on-times for a number of positive pulses that occur during the interval between sample signals. When a positive pulse arrives at the control input to switch IC 1A, a constant-current source charges capacitor C1 through IC 1A for the duration __ Circuit Design by Richard Nachazel, Vista Electronics Co, Ramona, CA

Circuit Detects voltage overrange - 10/10/96 EDN Design Ideas: Sometimes, a visual indication of whether a sensed voltage is above or below its nominal value can be useful. Most approaches to overvoltage or undervoltage sensing use two voltage comparators and a resistor divider to form a win __ Circuit Design by Mark Stitt, Burr-Brown, Tucson, AZ

Circuit disconnects load - 02/17/00 EDN Design Ideas: Placing a load-disconnect circuit on the output of a bootstrapped step-up regulator allows the regulator to start with load currents much higher than would otherwise be possible (Figure 1). During shutdown, the disconnect completely isolates the battery __ Circuit Design by Larry Suppan

Circuit Disconnects Load From Low-Voltage Supply - 04/24/03 EDN Design Ideas: Circuit ensures safety in power-on operation. Power supplies often include a circuit that disconnects the load when the supply voltage drops too low, such as when a battery is nearly discharged. A p-channel MOSFET connected between supply and load is the typical approach. However, a 1.5V single-cell battery or other low-voltage supply is insufficient to fully turn on the MOSFET. For such low-voltage systems, consider the circuit of Figure 1. __ Circuit Design by Steve Caldwell

Circuit Provides 1.5V, 7A Bus Termination - EDN Design Ideas: 09/14/95 Some of the newest high-performance processors require a 1.5V bus terminator that can source currents as high as 7A. This terminator requires a very fast transient response, because the device must react to high peak-current changes that have extremely fast rise times. The 1.5V terminator circuit in Fig 1 meets these demanding requirements. __ Circuit Design by Chester Simpson and Mineo Yamatake, National Semiconductor, Santa Clara,CA

Circuit safely applies power to ICs - 11/22/01 EDN Design Ideas: Supervisory circuits normally monitor a microprocessor's supply voltage, asserting reset to the IC during power-up, power-down, and brownout. in this way, the circuit ensures that the supply voltage is stable before the microprocessor boots, thus preventing code-execution errors. Many analog and digital ICs also need a well-behaved start-up of their supply to avoid latch-up and logic-stat __ Circuit Design by Clayton Grantham, National Semiconductor, Tucson, AZ

Circuit Serves as Milliohm Meter - 04/15/04 EDN Design Ideas: When I was recently debugging a design, I discovered that a short circuit existed from a ground plane to a power plane. I did not have access to a milliohm meter or an equivalent tester for locating this type of short circuit. So, I logged onto the internet to find an easily constructible milliohm meter __ Circuit Design by AM Hunt, Lancaster Hunt Systems Ltd, Shepperton, UK

Clamping dissipates minimal power - 03/30/00 EDN Design Ideas: The circuit in Figure 1 is a quasi-linear regulator. it functions as a source follower for input voltages greater than a preset level, determined by VR3. For input voltages lower than the preset level, the pass element, Q2, operates. PDF contains multiple circuits, scroll to find the one of interest __ Circuit Design by Carlisle Dolland, Allied Signal Aerospace, Torrance, CA

Cockcroft Walton Diode Voltage Multipliers - These circuits generate high voltages and can cause dangerous shocks! Do not build these devices unless you are experienced and qualified to work on high voltage devices. __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Contactless AC Mains Voltage Detector - This is a CMOS
IC (CD4033) based circuit which can be used to detect presence of AC mains voltage without any electrical contact with the conductor carrying AC current/voltage. Thus it...__ Electronics Projects for You

Dashboard Digital Voltmeter Project - This project is heLPFul to anyone who drives an automobile. I had found this project at the local libary. in an old publication. I made it and it worked fine. Below are the complete text and schematic of the Dashboard Digital Voltmeter. I re-typed the text and re-drew the schematic. as the printing from the book was old and faded. Sit back and read the story why this LED display might just save you from being stranded on the road! __ Designed by braincambre500 @ yahoo.com

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